1. Field of the Invention
The present invention primarily relates to an image processing apparatus that performs a process of rotating image data.
2. Description of the Related Art
In an image scanner apparatus, a copier, a facsimile machine, and an Optical Character Reader (OCR), or the like, when an original document is scanned in an inclined state, an inclined image is acquired, thereby deteriorating the scanning quality. In order to prevent such a deterioration, an image scanning apparatus that can electronically correct the inclination by performing a process of rotating image data has been disclosed.
It is commonly known that such an image rotating process uses a rotation matrix. Assuming that the coordinates of an arbitrary pixel of an original image is (x, y), and the coordinates of a corresponding pixel of a converted image is (x*, y*), for example, it is known that an image is rotated by using a formula represented in FIG. 1. Moreover, it is known that in a geometric correction process of an image including the above-described rotating process, a tone value (pixel value) of an intermediate pixel can be acquired by performing a two-dimensional interpolation process.
However, in such a method, multiplication of “sin θ” and “cos θ”, which are normally a surd, is performed with respect to each pixel, thereby substantially increasing the cost and time of calculations. Accordingly, a considerably long period of time is required for such an image rotating process, and when the process is applied to inclination correction of an image scanning apparatus, high-speed scanning cannot be easily performed.